Why Sleep

Why Do We Sleep?

And what the cuss are dreams for?

Circadian Rhythm• Any rhythmic change that continues at close to

a 24-hour cycle in the absence of 24-hour cues– body temperature– cortisol secretion– sleep and wakefulness

• In the absence of time cues, the cycle period will become somewhat longer than 24 hours

Circadian Rhythms

Electroencephalogram (EEG)

• Electrodes placed on the scalp provide a gross record of the electrical activity of the brain

• EEG recordings are a rough index of psychological states

EEG Waves of Wakefulness

• Awake, but non-attentive - large, regular alpha waves

1 second

Alpha waves

Awake, nonattentive

1 second

Beta waves

Awake, attentive

• Awake and attentive - low amplitude, fast, irregular beta waves

Stages of Sleep

• Sleep stage 1 - brief transition stage when first falling asleep

• Stages 2 through 4 (slow-wave sleep) - successively deeper stages of sleep

• Characterized by an increasing percentage of slow, irregular, high-amplitude delta waves Delta waves

Sleep stage 11 second

Sleep stage 4

Sleep stage 2

Spindlers (bursts of activity)

Stages of Sleep• Upon reaching stage 4 and after about 80 to 100

minutes of total sleep time, sleep lightens, returns through stages 3 and 2

• REM sleep emerges, characterized by EEG patterns that resemble beta waves of alert wakefulness– muscles most relaxed

– rapid eye movements occur

– dreams occur

• Four or five sleep cycles occur in a typical night’s sleep - less time is spent in slow-wave, more is spent in REM

Sleep: Stages

SW and REM Sleep

Sleep Cycles (8 hrs.)

REM Sleep• REM: rapid-eye movement

• lots of brain activity - EEG shows low voltage fast waves

• postural muscles are most relaxed during REM sleep

• loose associative thinking

• PGO waves - start in the pons geniculate nucleus of thalamus occipital cortex

REM Sleep

• neurons within the pons send inhibitory messages to the spinal cord during REM sleep

• this message inhibits motor neurons that project to large muscles

• REM sleep is still observed after damage to the pons

• but, no inhibition of muscle neurons…

Composition of Sleep over Lifespan

Is Sleep Adaptive?

• We are vulnerable during sleep.– Sense perception is

diminished– Reaction times delayed– Attention not on our

environment

• How can sleep help us survive and procreate?

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Repair and Restoration Theory

• Sleep enables the body and brain to repair itself after working hard all day

• Going without sleep causes people to be irritable, dizzy, and to have hallucinations and impaired concentration

• Sleep-deprived rats’ bodies work harder• Rats eventually die from sleep deprivation• Not true for other species

Is Sleep Something All Brains Need?

• Dolphins engage in “unihemispheric” sleep, where one half of the brain sleeps while the other half is awake.

• The fact that dolphins have developed this remarkable specialization suggests that sleep is pretty important that cannot be eliminated.

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Other Theories

• Neural Reset– The brain needs to be taken “off line” in order to

allow neuronal thresholds to return to baseline.

• Memory and Learning– Sleep may be a good time for integrating new

memories and learning without interference from ongoing activities.

Other Theories

• Sleep can be considered a state of adaptive inactivity that conserves resources during times when wakefulness is not an advantage.

• In humans, the brain constitutes 2% of total body weight, but consumes 20% of the energy.

Evolutionary Theory

- we evolved to sleep so that we would conserve energy when we were least efficient

- during sleep body temperature decreases

- predicts that species will sleep different amounts depending on how much they must look for food and watch for predators

Why Sleep?

Why Dream?

Activation-Synthesis Hypothesis

• dreams begin with episodic bursts of spontaneous activity in the Pons (PGO waves)• these PGO waves partially activate certain regions of the cortex• this haphazard input is combined with previous (waking) input• cortex “synthesizes” a story to make sense of all the input it is receiving

Sleep Disorders

Night Terrors• experience of intense anxiety from which a person awakens screaming in terror• occur during nonREM sleep• more common in children

Sleep Walking• occurs mostly in children• runs in families• expressed early in the night during stage 3 and 4 sleep

Individual Differences in Sleep Drive

• Some individuals need more and some less than the typical 8 hours per night

• Nonsomniacs - sleep far less than most, but do not feel tired during the day

• Insomniacs - has a normal desire for sleep, but is unable to and feels tired during the day

Sleep Disorders• Somnambulism - sleepwalking• Nightmares - frightening dreams that wake a

sleeper from REM• Night terrors - sudden arousal from sleep and

intense fear accompanied by physiological reactions (e.g., rapid heart rate, perspiration) that occur during slow-wave sleep

• Narcolepsy - overpowering urge to fall asleep that may occur while talking or standing up

• Sleep apnea - failure to breathe when asleep

Dreams and REM Sleep

• Everyone dreams several times a night– true dream - vivid, detailed dreams consisting

of sensory and motor sensations experienced during REM

– sleep thought - lacks vivid sensory and motor sensations, is more similar to daytime thinking, and occurs during slow-wave sleep

Dreams and REM Sleep• What are true dreams for? • Although research has yet to answer this

question, a prevalent view today is that dreams don’t serve any purpose at all, but are side effects of REM– to exercise groups of neurons during sleep– some are in perceptual and motor areas

• REM occurs in other mammals and to a much greater extent in fetuses and infants than adults

• REM sleep may help consolidate memories

Brain Mechanisms Controlling Sleep

• Sleep is promoted by a complex set of neural and chemical mechanisms

• Daily rhythm of sleep and arousal– suprachiasmatic nucleus of the hypothalamus– pineal gland’s secretion of melatonin

• Slow-wave sleep– raphe nuclei of the medulla and pons and the secretion of serotonin

• REM sleep– neurons of the pons

Language of The Dream

• Freud– Wish fulfillment– Protect sleep

According to Freud, dreams were disguised, hallucinatory fulfilment of repressed wishes.

He also asserted that dreams not only represented current wishes,

but were also invariably expressions of wish-fulfilments dating from early childhood.

Dreams, he believed,

gave indirect

expressions to

infantile sexual

wishes which had

been repressed and

which,…

if expressed in

undisguised form,

would so disturb

the dreamer that

he would wake

up.

Because these wishes are unacceptable and potentially disturbing, they are censored and disguised.

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REM Sleep• REM: rapid-eye movement

• lots of brain activity - EEG shows low voltage fast waves

• postural muscles are most relaxed during REM sleep

• loose associative thinking

• PGO waves - start in the pons geniculate nucleus of thalamus occipital cortex

Emergent Properties

• …are systemic features of complex systems which could nto be predicted …from the standpoint of a pre-emergent stage, despite a thorough knowledge of the features of, and laws governing, their parts.

Epiphenomenon

• Saying that dreams are designed to express unexpressed wishes is like saying bananas were designed to fit the human hand.

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Function of The Dream• Jung

– Compensatory function• Correcting biases of the conscious mind• Jung’s “crick in the neck” dream

– Prospective function• Agrees with Freud that dreams may look

backward• But they also may provide a vision of the

future• Jung’s dreams foreshadowing WW I

Interpreting The Dream• Freud

– Free association• Jung

– Critical of free association• Always goes back to childhood• Always leads to neurotic “hang-ups” (i.e. complexes)

– Amplification• Must begin with an open mind, willingness to discover

something new• Examine context of the dreamer’s life• Amplification keeps circling around the dream image

– Personal associations– Functional associations– Mythical, archetypal, literary, anthropological, and historical

associations

Interpreting The Dream, Cont.• Jung, Cont.

– Objective vs. Subjective level of meaning• The dream is a theater “in which the dreamer is himself the scene, the

player, the promoter, the producer, the author, the public, and the critic…”

– Active Imagination• Dreaming the dream onward• Dialoguing with the dream and/or dream elements• Giving concrete expression to the dream, e.g. painting, poetry, dance,

etc.

– Interpretation of archetypal symbols• No fixed meanings to symbols. No “dream books.”• Archetypal symbols with universal meanings transcending individual’s

consciousness• Archetypes not specific images but blueprints for images that are filled

in with material from individual’s life

The Break Between Jung and Freud

• Breaking point was Jung’s belief in archetypal symbols • 1909 trip to Clark University in the U.S. to receive honorary degrees• They share dreams on the steamship trip across the Atlantic

– Jung’s dream: Finds himself in second story of a house which he feels is his house; going down to ground floor, he sees medieval furniture and decorations. He then follows a stone stairway down to the cellar, which turns out to be from ancient Rome. Finds a stone slab in the floor, opens it, and descends into a dark cave strewn with bones and the remains of a primitive culture. On the dusty floor of the case, he sees two human skulls, very old and half disintegrated.

– Freud saw this dream as a primitive death wish against Jung’s parents

– Jung saw the dream as a structural diagram of the human psyche, showing a collective unconscious below the personal unconscious